The present invention relates generally to an ignition system in an air-cooled engine, and more particularly to such an ignition system involving a magnetic coil disposed adjacent the engine flywheel and interacting with a permanent magnet mounted on the flywheel.
Modern small engines of the air-cooled variety often employ solid state ignition modules which are compact and reliable and which require virtually no maintenance due to the absence of ignition breaker points or other parts subject to wear. Such an ignition module involves, among other things, a magnetic coil whose core is located adjacent the engine flywheel. Attached to the flywheel is a permanent magnet positioned so as to periodically encounter and interact magnetically with the magnetic coil core as the flywheel rotates. This periodic interaction governs the generation and timing of a high voltage electrical potential which is applied to the engine spark plug for combustion ignition.
U.S. Pat. No. 4,375,794 shows an ignition module of the type described above which includes a generally E-shaped laminated magnetic core having three legs located substantially in the plane of the flywheel and disposed adjacent the periphery of the flywheel. One difficulty that has been noticed with this arrangement is that air flow induced by the rotating flywheel carries debris which can become lodged around the ignition module and its mounting. Since the ignition module in this position is usually covered by a blower housing, the accumulation of debris in the vicinity of the ignition module is exacerbated and removal of the debris is complicated by the necessity of removing the blower housing first. Another difficulty which has been noted with respect to the prior art is the problem of accurately setting the arcuate air gap between the legs of the core and the periphery of the flywheel. It can be a difficult adjustment to make when it is desired that the legs be radially equidistant from the flywheel.
It would be desirable to provide an arrangement of an ignition module proximate the flywheel wherein the accumulation of debris thereabout is reduced and adjustment and service of the ignition module is facilitated. Such desirable results are obtained by the present invention.